Milo g



(No, Model.)

M. G. KELLOGG.

MULTIPLE SWITGHBOARD Patented Oct 26,1897.

IINTTED STATES PATENT FFICE.

MILO G. KELLOGG, OF CHICAGO, ILLINOIS, ASSIGNOR TO THE KELLOGGSIVITOIIBOARD AND SUPPLY COMPANY, OF SAME PLACE.

MULTIPLE SWITCHBOARD.

SPECIFICATION forming part of Letters Patent No. 592,348, dated October26, 1897.

Application filed anuary 2, 1890- Z'o all whom it may concern:

Be it known that I, MILO G. KELLOGG, of Chicago, in the county of Cookand State of Illinois, temporarily residing at Stuttgart, in the Empireof Germany, have invented certain new and useful Improvements inMultiple Switchboards for Telephone-Exchanges, of which the following isa full, clear, concise, and exact description, reference being had tothe accompanying drawings, forming a part of this specification.

My invention relates to a telephone-exchange system in which the linesare singlecircuit lines grounded at their outer ends; and it consists ina system of testing the lines to determine whether they are in use.

In the drawings illustrating my invention, Figures 1 and 1 representsections of two multiple switchboards of the exchange .to which the samelines are connected. Fig. 2 shows a diagram of the boards with themainline apparatus and connections necessary to illustrate my invention.Fig. 2 is a detail view of one of the line-annunciators. Fig. 3 shows adiagram of an operators cord system to be used in connection with theboards. Fig. a shows an operators test system to be used at the boards.

In Fig. 2, A is a sectional view of the switch board shown in Fig. 1,and A is a sectional view of the switchboard shown in Fig. 1", each asindicated by the line d c.

I place as many boards in the central office as are found necessary ordesirable in order to properly operate the exchange. On each board is aspring-jack orothersuitable switch for each line. Each switch has acontactspring which normally connects with an insulated contact-pieceand is adapted to receive a loop-plug and, when aplug is inserted, todisconnect the spring from the contactpiece and connect the twocontact-pieces of the plug with the spring and said insulatedcontact-piece, respectively. The switch is also adapted to receive asingle contact switchplug and, when a plug is inserted, to disconnectthe spring from the contact-piece and connect the spring with thecontact-piece of the plug. In the construction of the switches as shownand as will hereinafter be described I prefer to have a contact-pointelectrically Serial No. 335,698. (No model.)

connected with the contact-piece and on which the spring normally bears,as there is less chance of poor connect-ion when the spring bears on apoint than when it bears on a surface adapted to be brought intoconnection with the plug-contacts.

In Fig. 2, g g represent the springs of the different switches, h h thecontact-points on which the springs normally bear, and jj thecontact-pieces of the switches connected with the points 71. h. Z Z arethe SWltOlbllOlGS. a b are the rubber strips on which the metalparts ofthe switches are mounted, as shown, and through the fronts of which arethe switchholesl l. The contact-piecesj j are so placed along one of thesurfaces of the plug-holes as readily to form connection with one of thecontact-pieces of the loop-plug. The holes Z Z are adapted to receivethe switch-plugs, (shown in Fig. 3 and marked D D,) and when a plug isinserted into a switch it raises the spring 9 from the contact-point h,and the spring 9 and contact-piece of the plug are in contact. Theseholes are also adapted to receive the loop-plug shown in Fig. 4, andwhen a plug is inserted into a hole it raises the spring of the switchfrom the contactpoint It, and the spring g and the contactpiece j of theswitch are in contact with the two contact-pieces of the plug,respectively.

to and o: are calling-annunciators, one for each of the lines shown.Each annunciator has a pairof contact-points normally (or when theannunciator does not indicate a call) in contact with eachother, butwhich are separated by the annunciator while it indicates a call. Thetwo contact-points of a pair are marked 19 and g, respectively. One ofthem, q, is a spring-contact, which is pressed by the annunciator-dropwhen the drop falls away from its corresponding contact-point p. Thecontact-point p is represented as an anglepiece which passes over thespring (1 and is in contact with the spring when the spring is notactuated by the annunciator-drop.

The annunciator is shown in detail in Fig. 2 The line runs to aninsulated bolt 0 at the top of the annunciator-plate 0, thence throughthe an nunciator-coil to the plate, and thence normally through springg, which is in electrical contact with the plate, to the insulatedangle-piece 19, against which spring q normally bears, and thence toearth.

Two lines are shown in the drawings, one marked line No. 1 and the otherline N o. 2. These lines are ordinary single-circuit lines grounded attheir outer ends and having at the subscribers stations any usual andappropriate subscribers station, apparatus. Each line passessuccessively through the pairs of contacts of its switches on theseveral boards, passing in each case to the spring first. It then passesthrough its line-annunciator and the pair of contact-points of theannunciator to the ground. The circuit of each line shown may thus betraced in Fig. 2.

In the operators cord system shown in Fig. 3, D D are the switch-plugsof a pair of cords. n n are the rubber insulations of the plugs, and m mare their contactpieces. These contact-pieces pass each to the bottom ofits plug. and are adapted to rest normally, or

when the plug is not in use, on the metal piece 0, which then connectsit with. the ground. Weights, as is usual, or similar devices may beused to bring the contact-pieces of the plugs into. contact with thepiece 0 and secure a good connection. adapted to be inserted into any ofthe switches at their board,and when a plug is inserted it. operatestheswitch, as above described.

The'plugs should be inserted so that the contact-piece m is in contactwith the spring g. The connections. of the lines might have beenreversed, so that the lines pass firstto the contact-piece j of each oftheir switches, and in that case the plugs should be inserted in such aposition that their contact-pieces formconnection with the piecesj ofthe switches. Y is. the looping-in switch for the pair of cords shown. Kis thecalling-key. R is a resistance-coil, and v is a clearing-outannunciator. t is the operators telephone, and B. is her call-. inggenerator or battery. The circuits are substantially as shown.

The two contact-pieces of the-plu gs are connected by flexibleconductors to the two le vers, respectively, of the looping-in switch.One of the pairs of contact-bolts of the switch is connected togetherthrough the clearingout annunciator and the other pair is connectedthrough the operators telephone. The lever of the calling-key isconnected to one of the cords, and the point of the key is groundedthrough the calling generator or battery. The resistance-coil is placedin the circuit of the other cord of the pair.

The operation of the system in connection with the switchboards will beapparent to those skilled in the art. It will readily be apparent thatwhen a line is switched by the insertion of a plug into its switch theline is disconnected from its normal ground at the centraloffice and isconnected into a circuit with thepair of cords and that theresistancecoil of the pair of cords is in itscircuit. Only onepair o1":cords. is shown, but the connection of such other pairs, with theiraccom- These plugs are panying apparatus as the operator may need, willbe apparent to those skilled in the art. To each pair of cords, with itsplugs, belong a looping-in switch, a resistance-coil, aclearing-outannunciator, and a calling-key. One telephone and one calling-generatorwill answer for her system of cords. The plugs should be inserted intothe switches oi. the lines, so that the calling-key is connected to thecircuit of the cords between the resistancecoil and the switch-pluginserted into the line whose bell it may be desired to ring. If desired,two calling-keys may be used for each pair of cords, one connected oneach side of the resistance-coil.-

In the operators test system shown in Fig. 4, .T is a loop test-plugadapted to be inserted into any of the switches, and when inserted tooperate them, as heretofore described. B is a test-battery, and S is atest receiving instrument. The battery and instrument are j connected ina loop which terminates in the 1 two contact-pieces of the plug. Eachoperator has one cord system and one test system, and they areconveniently mounted and arranged for her work.

The test receiving instrument and battery are so constructed and relatedto each other that when they are looped into the circuit 1 with any lineand the circuit is not open at same pair of contact-points and does nothave the resistance-coilin its circuit the instrument Will sound orrespond, but when the circuit is open at any point or has theresistance-coil 1 connected as described in it the instrument will notsound or respond.

The operation of the test system is as follows: When an operator desiresto test a line, she places her test-plug into the switch of the line andby so doing disconnects the pieces g 1 and j of the switch and connectsthem with the contact-pieces of the plug. If, then, the i line is notswitched at any switch and its annunciator does not indicate a call, theinstrument and battery are on a closed circuit with the line and theinstrument will sound or respond, indicating that theline is free to beconnected to. If, however, the line-annunciator' indicates a call, (andthe line is not switched,) the circuit is open at the pair ofannunciator contact-points and the instrument will not sound. If, again,the line is switched at any board when the test is made and the switchin which the test is made is in the cutoff portion of the line, or thatportion which is between the switch used for switching and the officeground, the test-circuit is open at the. pair of contacts 9 71. of theswitch used for switching and the test receiving instrument wil notsound. If, again, the line isswitched a switch which is between the oneused and the subscribers station, the test-circuit has the resistance ofthe resistance-coil in circuit with the line and the instrument will notsound. When a test of a line is made and ithe test receiving instrumentsounds or reat any board and the test-plug is inserted into sponds, theoperator therefore knows that neither the line is switched for use atany board nor its annunctator indicates a call and that she may connectthe line with another. When she makes the test and the instrument doesnot sound, she knows that either the line is switched for use at someboard or its annunciator indicates a call, and she will not connect itwith another line. By this system of switching and testing a subscribersline tests busy when it is switched and when his annunciator indicates acall. His line is reserved to himself as soon as he has sent in a calland will not be switched with another line before his operator has hadtime to answer his call to his confusion and annoyance. In this system,also, there are only two contacts for each line on each board instead ofthree or more,as in other systems with groundcircuit lines, and there isonly one wire lead ing in and one leading out from each switch insteadof three or more in other systems. There is also but one wire betweenany two boards for each line instead of two or more, as in othersystems.

I claim as myinvention and desire to secure by Letters Patent- 1. In atelephone-exchange system, a telephone line normally passingsuccessively through pairs of switch contact-points, one pair on each ofseveral boards, each pair normally closed but open while the line isswitched at their board, and through a pair of annunciatorcontact-points norm ally closed but open while the annunciator indicatesa call, in combination with switching devices at each board todisconnect said pair of contact-points at the board and switch the linefor conversation with a resistance coil switched into the circuit, and aloop test-plu g in the two contact-pieces of which terminate the twosides of a loop containing a test receiving instrument and battery, saidloopplug being adapted to be inserted into a switch and when inserted todisconnect said pair of contact-points of the switch which are normallyin contact and connect them with the two contact-pieces of the plug,said battery and instrument being so related and adj usted that theinstrument sounds when looped into the closed circuit of the linewithout the resistance-coil, but does not sound when the resistance-coilis included in the circuit, substantially as set forth.

2. In a telephone-exchange system, a telephone-line grounded at itsouter end and normally passing, successively, through pairs of switchcontact-points, one pair on each of several boards, each pair normallyclosed but open while the line is switched at their board and through apair of annunciator contactpoints normally closed but open while theannunciator indicates a call and thence to the ground, in combinationwith switching devices at each board to disconnect the pair ofcontact-points at the board and switch the line for conversation with aresistance-coil switched into the circuit, and a loop testplug in thetwo contact-pieces of which terininate the two sides of a loopcontaininga test receiving instrument and battery, said plug beingadapted to be inserted into a switch and when inserted to disconnectsaid pair of contact-points of the switch which are normally in contactand connect them with the two contact-pieces of the plug, saidinstrument and battery being so related and adjusted that the instrumentsounds when they are looped into the closedcircuit of thc line but doesnot sound when the resistancecoil is included in the circuit,substantially as set forth.

3. In a telephone-exchange system, a telephone-line normally on closedcircuit and passing successively through pairs of switch contact-points,one pair on each of several boards, each pair normally closed but openwhile the line is switched at their board and through a pair ofcontact-points of the lineannunciator normally in contact but open whilethe annunciator indicates a call, in combination with switching devicesat each board to disconnect the pair of contact-points at the board andswitch the line for conversation with a resistance-coil then switchedinto the circuit, and a loop test-plug in the two contact-pieces ofwhich terminate the two sides of a loop containing a test receivinginstrument and battery, said plug being adapted to be inserted into theswitches and when inserted into a switch to disconnect its said pair ofcontact-points and connect them with the two contact-pieces of the plug,said instrument and battery being so related and adjusted that theinstrument sounds when they are looped into the simple closed circuit ofthe line but will not sound when the resistance-coil is included,substantially as set forth.

4. In a telephone-exchange system, a telephone-line grounded at itsouter end and passing normally successively through pairs of switchcontact-points, one pair on each of several boards, each pair normallyclosed but open while the line is switched at their board, and through apair of contact-points of the line-annunciator normally in contact butopen while the annunciator indicates a call, and thence to the ground,in combination with switching devices at each board to disconnect thepair of contact-points at the board and switch the line for conversationwith a resistancecoil then included in the circuit, a loop test-plug inthe two contact-pieces of which terminate the two sides of a loop whichcontains a test receiving instrument, said plug being adapted to beinserted into the switches and when inserted into a switch to disconnectits said pair of contact-points and connect them with the twocontact-pieces of the plug, and battery in the test-circuit therebyestablished, said instrument and battery being so related and adjustedthat the" instrument sounds when they are looped into the simple closedcircuit of the line but will not sound when the resistancecoil isswitched into circuit with the line, substantially as set forth.

5'. In a telephone-exchange system, 'a telephone-line normally on closedcircuit and passing successively through pairs of switch contact-points,one pair on each of several boards, each pair normally closed but openwhile the line is switched at their board, and through a pair ofcontact-points of the lineannunciator normally in contact but open whilethe. annunciator indicates a call, in combination with switching devicesat each board to disconnect the pair of contact-points at the board andswitch the line for conversation with a resistance-coil then switchedinto circuit. with it, a loop test-plug in the two contact-pieces ofwhich terminate the two sides of a loop which contains a test receivinginstrument, said plug being adapted to be inserted into the switches andwhen inserted into a switch to disconnect its said pair ofcontact-points andi'connect them with the two contact-pieces of theplug, and battery in the test-circuit, thereby established, saidinstrument and battery being so related and adjusted that the instrumentsounds when they are looped intolthe simple closed circuit of the linebut will not sound when. the resistance-coil is switched into circuitwith the line, substantially as set forth.

6. In a telephone-exchange system, a telephone-line normally on closedcircuit and havin g in its circuitpairs of switch contact-points, one.pair on each of several boards, each pair normally closed but open whilethe line is switched for use at its board and having in its circuitapai'r of annunciator contact-points normally closed but open while theannunciator indicates a call, in combination with switching devices ateach board to disconnect said pair of contact-points-atv the board andswitch the line for conversation with a resistance-coil then switchedinto circuit with it, and loop test-plugs, one at each board, each plughaving two contact-pieces in which terminate the two sides of a loopcontaining a test receiving instrument and battery and adapted to beinserted into the switch of the 5 line, at its board, and when insertedto disconnect said pair of contact-points which are normally in contactand connect them with the two contact-pieces of the plug, eachinstrument and its battery beingso related and adjusted that theinstrument sounds when they are looped into the simple closed circuit,of the line; but will not sound when they and the resistance-coil areswitched int-o circuit with the line, substantially as set forth.

Z. In a telephone-exchange, system, a telephone-line normally on closedcircuit and 1 having in its circuit pairs of switch contactpoints, onepair oneach of several boards,

each pair normally closed but open while the line is switched for use attheir board and having in its circuit a pair of contact-points of itsannunciator, normally closed but open while the annunciator indicates acall, in combination with switching devices at each board to disconnectthe pair of contact-points at the board and connect the-line forconversation with a resistance-coil then switched into circuit with it,and loop test-plugs, one at each board, each plug having twocontactpieces in which terminate the two sides of a loop-which containsa test receiving instrument and adapted to be inserted into the switchof the line at its board and when inserted to disconnect the pair ofcontactpoints which are normally in contact and connect them with thetwo contact-pieces of the plug, and a battery in the circuit establishedon testing, each instrument and the battery being so related andadjusted that the instrument sounds when they are looped into the simpleclosed circuit of the line but will not sound when they and theresistancecoil are switched into circuit with the line, substantially asset forth.

8. In a telephone-exchange system, multipleswitchboards,telephone-lines,switches for said lines, one switch on eachof the boards for each line, each switch having a pair of contact-pointsnormally in contact but open while a switch-plug is inserted,line-annunciators, one for each line, each annunciator having a pair ofcontact-points normally in contact but open while the annunciatorindicates a call, each line passing successively through said pairs ofswitch contact-points of its switches and through its annunciator andthe annunciator contact-points, in combination with pairs ofswitch-plugs atv each board, the contact-pieces of each pair beingconnected by flexible conductors containing a resistance-coil in theircircuit, said plugs being adapted to be inserted into the switches at,their boards and when inserted into aswitch to disconnect the pair ofcontact-points of the switch and connect the line contact- ;point of theswitch with the plug con-tactpiece, and loop test-plugs, one at eachboard, each plug having two contact-pieces in which terminate the twosides of a loop containing a test receiving instrument and battery andadapted to be inserted into any switch at its iboard and when insertedinto a switch to disconnect the contact-points of the switch and connectthem with the contact-pieces of the plug, each instrument and itsbattery being so related and adjusted that when they are looped into thesimple closed circuit of t any line they will sound but will not soundiwhen they and one of said resistance-coils 2 are in circuit with theline, substantially as set forth. 7

9. In a telephone-exchange system, multilple switchboards,telephone-lines, each line L being normally on a closed circuit,switches for said lines, one switch on each of the boards for each line,each switch having a pair of contact-points normally in contact and openwhile a switch-plug is inserted into it, lineannunciators, one for eachline, each annunciator having a pair of contact-points normally incontact but open while the annunciator indicates a call, each linepassing normally successively through said pairs of contact-points ofits switches on the several boards and through its annunciator and thecontact-points of the annunciator, in combination with pairs ofswitch-plugs at each board, the contact-pieces of each pair beingconnected by a flexible conductor containing a resistance-coil in thecircuit, said plugs being adapted to be inserted into the switches attheir boards and when a plug is inserted into a switch to disconnect thepair of contact-points of the switch and connect the line contact-pointof the switch with the plug contact-piece, and loop test-plugs, one ateach board, each plug having two contact-pieces in which terminate thetwo sides of a loop containing a test receiving instrument and battery,and adapted to be inserted into any switch at its board and wheninserted to disconnect the contact-points of the switch and connect themwith the contact-pieces of the plug, each instrument and its batterybeing so related and adjusted that when they are looped into the simpleclosed circuit of any line the instrument will sound but will not soundwhen the instrument and battery are included in the circuit of the lineand any of said resistance-coils, substantially as set forth. 7

10. In a telephone-exchange system, multiple switchboards,telephone-lines, each line being normally 011 closed circuit, switchesfor said lines, one switch on each of the boards for each line, eachswitch having a pair of contact-points normally in contact but openwhile a switclrplug is inserted into it, lineannunciators, one for eachline, each annunciator having a pair of contact-points normally incontact but open while the annunciator indicates a call, each linepassing normally successively through said pairs of contact-points ofits switches on the several boards and through the annunciator and thecontact-points of the annunciator, in combi nation with pairs ofswitch-plugs at each board, the contact-pieces of each pair beingconnected by flexible conductors which contain a resistance-coil intheir circuit, said plugs being adapted to be inserted into the switchesand when a plug is inserted into a switch to disconnect said pair ofcontactpoints and connect the line contact-point with the contact-pieceof the switch, and loop testplugs, one at each board, each plug havingtwo contact-pieces in which terminate the two sides of a loop whichcontains a test receiving instrument, and adapted to be inserted intoany switch at its board and when inserted to disconnect thecontact-points of the switch and connect them with the contact-pieces ofthe plug, and a battery in any test-circuit established on testing, eachinstrument and battery being so related and adjusted that when they arelooped into the simple closed circuit of any line the instrument willsound but will not sound when they are included in a circuit whichcontains the line and either of said resistance-coils, substantially asset forth.

In witness whereof I hereunto subscribe my name this 13th day ofDecember, 1889.

MILO G. KELLOG G.

\Vitn esses EMIL ,ABENHEIM, MARGARETHA RIEHL.

